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This is old circuit Power amp OCL, But easy circuit and very nice. To use for play music in your home. It low cost too. It use IC 741 or LF351(good) and Transistor x 4 (2N3055+MJ2955+BD139+BD140) and little component. Power supply volt +35V/-35V and 3A for Mono, 5A for Stereo.

This is DAC with integrated circuit PCM1794A. It is one of excellent audio DACs from Burr Brown (Texas Instruments). It has 24-bit resolution, 192kHz sample frequency, 8x oversampling digital filter, differential current output and SNR 127dB.

The following is a simple USB DAC Soundcard. It uses PCM2707 that incorporates USB interface to communicate with the computer and audio DAC all in one chip.

Many of us have a pair of headphones connected to the output of the computer sound card us either to enjoy songs, or a game. Very likely your headphones and microphone, which also connect to the appropriate slot your sound card. But at some point broke down the female plug my sound card, and because quite a lot to change the plug when I put the headphones and when the speakers. A small structure is a sound card, USB, with stereo inputs / outputs, button to increase / volume button for volume and mute! When connected Windows will recognize as a sound card! With all the materials to be SMD, the cornered enough and fit into a small plastic box, which by one measure has a cable with USB plug, sound to go acoustic (Left / Right) and condenser microphones. The supply of (as imagined) is done by the USB port. The heart of the integrated circuit is PCM2902 of Burr-Brown by Texas Instruments. It is stereo 16-bit DAC and ADC, fully compatible with USB 1.1. DAC sampling frequencies are 32, 44.1 and 48 kHz, ADC has 8, 11.025, 16, 22.05, 32, 44.1 and 48 kHz. If you want more sound intensity, you will need to connect TDA 7050 amplifier to audio output.

This DAC is based on latest 32bit/384K PCM5102 DAC chip and DIR9001 from Texas Instruments. Sound quality produced by PCM5102 DAC is surprisingly good, very smooth and airy, with great dynamics and excellent soundstage. It features both S/PDIF and optical inputs connected to DIR9001 low jitter digital receiver. PCM5102 uses a next generation architecture based on the PCM1792/4 TI's flagship DACs. It has 112dB SNR, with an integrated negative rail charge pump and line driver, so you don't need no opamps at the end or dual split supplies. Just a simple RC low pass filter is all that is needed. In addition, there's a fancy PLL involved that will autodetect I2S rate, configure the device, and generate it's own internal master clock so no need for external clock. Entire DAC is powered by only 3.3V from 1117-33 regulator and consumes only 20mA of power. Although PCM5102 DAC can be powered by 4-12V DC voltage, it's recommended to power it from a single 3.7V LIPO battery to achieve the best performance.

Portable Headphone Amplifier powered by just 3 Volts. Notes: * Can be directly connected to CD players, tuners and tape recorders. * Tested with several headphone models of different impedance: 32, 100, 245, 300, 600 & 2000 Ohm. * Schematic shows left channel only. * B1, SW1, J1 & C3 are common to both channels. * R3 value was calculated for headphone impedance up to 300 Ohm. Using 600 Ohm loads or higher, change R3 value to 100K.

This little tube amplifier is easy to build and will fit into a small metal Altoids box and can be carried around. It can be build with few common parts, that should be readily available. Amplifier works with many tubes like 6DJ8, ECC88, 6922, 12AT7, 12AX7, DAF96, 1T4, etc. It is powered by 12V supply and power consumption may be optimized to allow for small rechargeable battery packs.

This new amp (like the original) is based on an amp I originally designed many years ago, of which hundreds were built. Most were operated as small PA or instrument amps, but many also found their way into home hi-fi systems. The amp is perfectly capable of driving 4 Ohms, provided the supply voltage is maintained at no more than ±35V.

The traditional potentiometer is implemented with an electrical contact that slides over a resistive layer. An example of a well-known audio-grade potmeter is the Alps Blue. I still use this one myself. A high-end (good and costly) alternative is the rotary switch. This device consists of a series of discrete resistors and switches, of which always one switch is actually closed. Resistor-switch networks can offer advantages over the potentiometer such as: * Improved quality of the electrical contact, in comparison with the slider. * Improved consistency between separate audio channels (stereo or multi-channel) * Less sensitive to dust and wear.

This is quite possibly the simplest S/PDIF receiver and DAC available. It uses the absolute minimum of parts, and also minimises the connections and control functionality usually provided. It is still a serious project, and is not recommended for beginners. As shown, the connection is COAX (but will almost certainly handle TTL just as well). If you want a dedicated TTL to COAX converter, there is an adapter shown at the end of this article. The spare gates in the 74HC04 package may be used for the adapter if desired.